Oscillating weight

ABSTRACT

An oscillating weight for an automatic watch is arranged to carry a bearing defining an axis of rotation (A—A) and is intended to be mounted on the frame of the watch. The mass member of the weight has a center of gravity (G) shifted with respect to the axis of rotation. In this weight, this mass member includes two parts that can be moved one ( 10, 18 ) in relation to the other ( 24 ), and arranged such that their relative movement causes a radial movement of the center of gravity (G) of the mass member. The mass member also has a securing device ( 13, 14, 16   b ) cooperating with the first and second parts, capable of occupying a first state in which the parts can be moved with reference to each other, and a second state in which the parts are rigidly secured to each other.

FIELD OF THE INVENTION

The present invention concerns automatic watches. It relates moreparticularly to oscillating weights.

BACKGROUND OF THE INVENTION

Automatic watches comprise a movement fitted with a time base, a geartrain synchronized by the time base, an energy accumulator, generally abarrel, powering the time base and driving the gear train, and anautomatic mechanism supplying energy to the energy accumulator.

Conventionally, this mechanism comprises an oscillating weight,pivotably mounted on the frame of the movement by means of a bearing, areverser converting the alternating movement of the weight into arotational movement in one direction, and a winding train, which is ofthe reduction train type, driven by the reverser. The oscillations ofthe weight, generated by the movements of the person wearing the watch,thus drive in rotation the winding train, which cooperates with thebarrel to wind its spring.

The oscillating weight is arranged to carry a bearing, for example aball bearing, which defines an axis of rotation. It comprises a massmember whose center of gravity is shifted with respect to the axis ofrotation. The mass member is generally designed so as to generatemaximum torque. It is made of a heavy material, frequently gold orplatinum in top of the range watches. At its periphery, it includes asector of inertia defining the important part of its weight, and a plateconnecting the sector to the bearing.

The oscillating weight generates torque essentially as a function of theweight of the sector and the position of its center of gravity, withreference to the axis of rotation. This torque is applied to the firstwheel set of the winding train via the reverser. The reduction rate ofthe gear train forming the winding train defines the torque finallyapplied to the barrel spring. When the person wearing the watch is acalm person, arm movements unpoise the weight and it is the terrestrialacceleration g which defines the torque. If the person is very active,the accelerations encountered can be substantially greater. Currently,winding mechanisms are chosen so as to provide spring winding conditionsfor a normally active person. Consequently, with a very active person,the barrel spring is greatly taxed and the risk of excessive wear cannotbe ruled out. If, conversely, the person wearing the watch is very calm,the spring barrel is not wound sufficiently.

SUMMARY OF THE INVENTION

It is an object of the present invention to allow peculiarities of theperson wearing the watch to be taken into account in order to improvewinding conditions. Therefore, the mass member includes:

-   -   two parts that can be moved in relation to each other, and        arranged such that their relative movement causes a radial        movement of the center of gravity of the mass member, and    -   a securing device, cooperating with the first and second parts,        capable of occupying a first state in which said parts can be        moved with reference to each other, and a second state in which        said parts are rigidly secured to each other.

Owing to the fact that the two parts can be moved in relation to eachother and with them, the center of gravity of the weight, it is possibleto vary the working conditions of the mechanism and thus adapt it to theuser's way of life.

Advantageously, the first part of the oscillating weight furthercomprises a plate, arranged for carrying the bearing, and a sector ofinertia. This plate extends from the center, which is provided with ahole in which the bearing is engaged, towards the periphery whichcarries the sector of inertia. Certain weights comprise an added sectorof inertia, while others are made in one piece.

In a first embodiment, the second part is formed of at least one inertiablock pivotably mounted on the sector. Moreover, the securing deviceincludes indexing means arranged for positioning the inertia block in afinite number of predefined positions in which the securing device holdsthe inertia block when it is in its second state, whereas it allowspassage from one of these positions to another when it is in its firststate.

In order to increase the correction range and/or the accuracy of suchcorrection, the second part comprises two inertia blocks.

In a variant allowing a high level of adjustment precision, one of theinertia blocks can occupy a finite number n of positions defined suchthat the passage of said inertia block from one of the positions toanother causes a radial movement of the center of gravity of a value ΔG,and so that the second inertia block is arranged so as to be able tooccupy a number m of positions where the passage from one position toanother causes a radial movement of the center of gravity of a value Δg,said inertia blocks being arranged such that the product m.Δg issubstantially equal to ΔG. Consequently, it is possible to define m.nadjustment positions, without the indexing means becoming too complex.

In this embodiment, the moment of inertia of the weight decreases withthe torque being generated.

In a second embodiment, the second part of the weight also includes aplate and a sector of inertia, disposed side by side respectively withthe plate and the sector of the first part. Moreover, the securingdevice is arranged so as to allow a relative movement of the second partwith reference to the first part by rotation about the axis of theoscillating weight.

Other advantages and features of the invention will appear from thefollowing description, made with reference to the annexed drawing. Thevarious features of novelty which characterize the invention are pointedout with particularity in the claims annexed to and forming a part ofthis disclosure. For a better understanding of the invention, itsoperating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 a is a top view in accordance with a first embodiment of theinvention;

FIG. 1 b is a cross-sectional view in accordance with the firstembodiment of the invention;

FIG. 1 c is an exploded view showing an oscillating weight in accordancewith the first embodiment of the invention;

FIG. 2 a is a plan view showing an oscillating weight in accordance witha second embodiment of the invention;

FIG. 2 b is a cross-sectional view showing an oscillating weight inaccordance with the second embodiment of the invention; and

FIG. 2 c is an exploded view showing an oscillating weight in accordancewith the second embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The weight shown in FIG. 1 includes a plate 10 comprising a centralportion 10 a of generally annular shape, provided with a centralaperture 10 b for receiving a bearing 12 that is partially shown, forexample a ball bearing, and arms 10 c extending radially outwards. Thecentral aperture 10 b is circular, defined by a circle of axis A—A.

In its central portion 10 a, plate 10 carries, arranged in a ring,threaded pins 13 for securing bearing 12 by means of bolts 14.

At their periphery, arms 10 c are connected by an annular center portion10 d disposed on axis A—A. It is provided with three holes in whichscrews 16 a are engaged.

A sector of inertia 18, in the form of an annular portion, is providedwith five threaded feet 20. It is secured to plate 10 by means of screws16 a engaged in three of threaded feet 20. It is advantageously made ofa heavy material, for example gold or platinum in top of the rangewatches, of brass for more common products. It extends over an angle ofapproximately 180°. The function of the two other threaded feet 20 willbe specified hereinafter.

Plate 10 is only secured to sector 18 over an angle of approximately90°, via its annular portion 10 d. The edges of arms 10 c connectingcentral portion 10 a to annular portion 10 d are also in the arc of acircle, the centers of which are each at one of the ends of sector 18,identical to the centers of the two other threaded feet 20. These edgeseach carry six regularly distributed threaded feet 22.

One of inertia blocks 24 is mounted on each of end feet 20. They havethe general shape of a sector of a circle and include, at the apex 24 aof the sector, a cylindrical hole in which threaded foot 20 is engaged,and a screw 16 b for axial holding. The opposite side is provided with afinger 24 b including an aperture to be engaged in one or other ofthreaded feet 22. A nut 26 is screwed onto foot 22 in order to holdinertia block 24 via its finger 24 b.

In this oscillating weight, the sector of inertia 18 and plate 10 form afirst part of a mass member, and inertia blocks 24 a second part, thecenter of gravity of said member being located at G. Screws 16, threadedfeet 20 and threaded feet 22, and nuts 26 act as the securing device,which, depending upon whether its constituent parts are in an unscrewedor screwed state, allows or prevents the movement of inertia blocks 24with reference to sector of inertia 18 and plate 10. Moreover, thethreaded feet index inertia blocks 24, so that the latter can occupy adetermined number of positions.

With the weight thus described, it is possible to vary by severalpercent the torque that it applies to the gear train in order to rewindthe motor spring of the watch. The position of one or other of the twoinertia blocks 24 has only to be altered. The center of gravity G isshifted further with respect to axis A—A and, consequently, the torqueis greater when the ends fitted with finger 24 b of inertia blocks 24are in proximity to sector 18. Conversely, by returning finger 24 b sothat it is engaged in a foot 22 close to central portion 10 a, thecenter of gravity if shifted towards axis A—A, so that the torque isreduced.

Any horologist trained for this purpose can adjust the torque. In orderto guarantee optimum working conditions, a first adjustment can be madewhen the watch is sold, by classifying the person that it is for withreference to his or her physical activities, both professional andleisure activities. On this basis, the instructions for the watch definethe position in which the inertia blocks should be located. Afterseveral days wear, it is possible to check whether the position selectedis correct. In order to carry out the adjustment, one has only tounscrew screws 16 b and nuts 26 to be able to move inertia blocks 24,then screw them back in again when inertia blocks 24 are in the chosenposition.

In order to make the most accurate adjustment possible, one couldenvisage using inertia blocks that do not have the same features. One ofthem can occupy a finite number n of positions defined such that passagefrom one position to another generates a radial movement of the centerof gravity of a value ΔG. The second inertia block is arranged so as tobe able to occupy a number m of positions where passage from oneposition to another generates a radial movement of the center of gravityof a value Δg. The inertia blocks are sized such that the product m.Δgis substantially equal to ΔG. Consequently, an accurate correction canbe made.

The embodiment described hereinbefore has to be only slightly altered inorder to achieve this result. The dimensions (thickness, lengthparticularly) of one of the inertia blocks have only to be reduced in anappropriate manner to obtain the desired effect. This operation iseasily accessible to those skilled in the art.

Adjustment can occur particularly easily in a watch fitted with a powerreserve. Then, one only needs to establish a correlation between themovement of the inertia blocks and the degree of winding of the spring.

In the embodiment described with reference to FIG. 1, the moment ofinertia increases at the same time that the center of gravity of theweight is moved. It is also possible to change the position of thecenter of gravity while keeping the same moment of inertia. This ispermitted by the embodiment shown in FIG. 2, which shows a weight shownin plan at 2 a and in cross-section at 2 b and blown up at 2 c.

This weight includes first and second parts 32 and 34 each including aplate and a sector of inertia, respectively referenced 36 and 38 for thefirst part 32 and 40 and 42 for the second part 34.

Plates 36 and 40 have the general shape of a sector of a circle, with anapex angle of approximately 45°. The apex part is cut to form an annularportion identified by the letter a, covering an angle of approximately200° for portion 36 a and approximately 90° for portion 40 a, as can beseen in FIG. 2 c. These portions are pierced with holes identified bythe letter b, three oblong holes in portion 36 a and two cylindricalholes in portion 40 a.

The two plates are assembled to each other by means of a securing devicecomprising a tightening ring 44 provided with threaded holes 44 a, andarranged below portions 36 a and 40 a, a cover 46 placed above portions36 a and 40 a, provided with cylindrical holes 46 a aligned on holes 44a, and screws 48 freely engaged in the holes of cover 46 and annularportions 36 a and 40 a, and tightened in threaded holes 44 a oftightening ring 44.

Since plate 36 is provided with oblong holes, it is possible to move itangularly with reference to plate 40, about an axis corresponding to thepivoting axis A—A of the weight, if screws 48 are unscrewed.

Plates 36 and 40 are each pierced with three holes identified by theletter c, made at the periphery of the sector of the circle. Theirfunction will be specified hereinafter.

Sectors of inertia 38 and 42 each include an annular portion, identifiedby the letter a and covering an angle of approximately 80°, and ashoulder b attached to the annular portion a in its concave part.Shoulder b, which extends over approximately 45, acts as a support forthe plate. It is provided with two cylindrical holes, identified by theletter c, in which are engaged, for each of them, a tightening stud 50,which is provided with a threaded hole. Two screws 52 are engaged in twoof holes c of plates 36 and 40 and in studs 50 in which they aretightened. Plates 36 and 40 are, consequently, respectively secured tosectors 38 and 42.

In a variant, sectors 38 and 42 could also be integral respectively withplates 36 and 40, or welded to each other.

With the structure that has just been described, it may happen thatplates 36 and 40 lack rigidity. Thus, in order to better secure the twoparts to each other, the securing device further includes a stiffeningarm 54, in the form of an annular portion covering an angle ofapproximately 90°, disposed in the extension of shoulders 38 b and 42 b.This arm includes two oblong apertures 54 a each disposed facing thethird hole of the plates. A screw 56, cooperating with a nut 58, isengaged in each of these holes and in holes 36 c and 40 c that are notoccupied by screws 52, such that, by tightening the screw and its nut,it is possible to secure the two parts rigidly to each other.

Numerous variants of the two embodiments described hereinbefore can ofcourse be envisaged. The solutions described largely rely on screws,which is a particularly simple solution to implement for making singlepieces or prototypes. In the case of large-scale manufacture, one couldenvisage using other locking systems, for example snap-fit systems, orany other means known to those skilled in the art. The two constituentparts of the weight could also have very different shapes, and havedimensional ratios that vary considerably, as a function of the relativemovement possible and the desired range of adjustment.

It would also be possible to design a weight in accordance with thesecond embodiment fitted with an inertia block as defined in the firstembodiment, so as to allow a rough adjustment with relative movement ofthe two parts, then a finer adjustment by adjusting the position of theinertia block.

Thus, owing to the fact that the weight according to the invention hastwo parts that are mobile with reference to each other, their movementinducing a change in radial position of its center of gravity, it ispossible to optimize the working conditions of automatic watches andthus obtain optimum yield for a minimum volume, whatever the conditionsimposed by the person wearing the watch.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

1. An oscillating weight for an automatic watch, arranged to carry abearing defining an axis of rotation and intended to be mounted on aframe of the watch, including a mass member having a center of gravityshifted with respect to the axis of rotation, said member comprising:two parts that can be moved one in relation to the other, and arrangedsuch that their relative movement causes a radial movement of the centerof gravity of the mass member, and a securing device cooperating withthe first and second parts, capable of occupying a first state in whichsaid parts can be moved with reference to each other, and a second statein which said parts are rigidly secured to each other.
 2. An oscillatingweight according to claim 1, wherein said first part includes a platearranged for carrying said bearing and a sector of inertia rigidly fixedto the plate.
 3. An oscillating weight according to claim 2, whereinsaid second part is formed of at least one inertia block pivotablymounted on said sector and in that said securing device includesindexing means arranged for positioning said inertia block in a finitenumber of predefined positions in which said device holds said inertiablock when said device is in its second state, whereas said deviceallows passage from one of these positions to another when said deviceis in its first state.
 4. An oscillating weight according to claim 3,wherein the second part includes two inertia blocks.
 5. An oscillatingweight according to claim 4, wherein one of the inertia blocks canoccupy a finite number n of positions, defined such that the passagefrom one of the positions to another generates a radial movement of thecenter of gravity of a value ΔG, and in that said second inertia blockis arranged so as to be able to occupy a number m of positions where thepassage from one position to another generates a radial movement of thecenter of gravity of a value Δg, said inertia blocks being arranged sothat the product m.Δg is substantially equal to ΔG.
 6. An oscillatingweight according to claim 2, wherein said second part also includes aplate and a sector of inertia, disposed respectively side by side withthe plate and the sector (38) of the first part, and in that thesecuring device is arranged to allow, in its first state, a relativeangular movement of the second part with reference to the first part byrotation about said axis.
 7. An oscillating weight for an automaticwatch, the weight comprising a mass element with a bearing portiondefining an axis of rotation and a remaining mass portion defining anouter radial extent, the mass element having a center of gravity shiftedradially outwardly with respect to the axis of rotation, the masselement comprising: a first part; a second part movable relative to thefirst part and arranged such that the relative movement causes a radialmovement of the center of gravity of the mass element, and a securingdevice cooperating with the first part and second part, said securingdevice occupying a first state in which said second part can be movedwith reference to said first part and a second state in which saidsecond part is rigidly secured to said first part.
 8. An oscillatingweight according to claim 7, wherein said first part includes a platearranged for carrying said bearing portion and a sector of inertiarigidly fixed to the plate.
 9. An oscillating weight according to claim8, wherein said second part is formed of at least one inertia blockpivotably mounted on said sector of inertia; and said securing deviceincludes indexing means arranged for positioning said inertia block in afinite number of predefined positions in which said device holds saidinertia block when said device is in its second state, whereas saiddevice allows said second part to be moved with reference to said firstpart from one of these positions to another when said device is in saidfirst state.
 10. An oscillating weight according to claim 8, whereinsaid second part includes two inertia blocks.
 11. An oscillating weightaccording to claim 10, wherein one of the inertia blocks can occupy afinite number n of positions, defined such that the passage from one ofthe positions to another generates a radial movement of the center ofgravity of a value ΔG, and in that said second inertia block is arrangedso as to be able to occupy a number m of positions where the passagefrom one position to another generates a radial movement of the centerof gravity of a value Δg, said inertia blocks being arranged so that theproduct m.Dg is substantially equal to ΔG.
 12. An oscillating weightaccording to claim 8, wherein said second part also includes a plate anda sector of inertia, disposed respectively side by side with the plateand the sector of the first part, and in that the securing device isarranged to allow, in said first state, a relative angular movement ofthe second part with reference to the first part by rotation about saidaxis.